UH Diesel Testing Facility to Measure Fuel Efficiency of Metro Buses

The Metropolitan Transit Authority of Harris County (Metro), with its large bus fleet, is no exception. For several
years, Metro has been adding diesel-electric hybrid buses to its fleet in an
effort to curb the transportation system’s fuels costs.

Exactly how much fuel Metro is saving with its hybrids is the question the
University of Houston has been asked to answer. Next month, UH’s Texas Diesel
Testing & Research Center will begin testing hybrid and regular Metro buses
for fuel efficiency.

“Metro’s bus vendors have outlined the
projected fuel costs savings of their buses, but the transportation system
wanted an independent verification of those figures,” said Rachel Muncrief, the
project’s lead investigator and a UH research assistant professor of chemical and
biomolecular engineering. “This two-year project is
essentially about fuel economy.”

The UH center is a comprehensive research facility
for the development and testing of advanced powertrain and emissions
after-treatment technologies for local, state and federal governments as well
as the fuels, engine and after-treatment industries. Staffed by researchers
from chemical and biomolecular engineering and mechanical engineering, the center’s
focus is on cleaner emissions, renewable fuels and increased fuel economy for
heavy duty diesel vehicles.

A diesel-electric hybrid bus is distinguishable
by a large, heavy battery attached on top of the vehicle. There are different
types of hybrid buses and the newer models come equipped with technology
designed to reduce nitrogen oxide (NOx) emissions.

Hybrid buses generally are more expensive to
purchase and they each weigh about 2,000 pounds more. Still, the long-term fuel
savings makes them a good investment. Hybrids also use regenerative brake
systems, which transfer some energy into the batteries when the brakes are
engaged, helping to recharge the batteries. This makes the buses easier to operate
because drivers don’t have to push as hard on the brakes.

For the Metro project, researchers will test
both hybrid and regular buses to get baseline information from each, and they
also will determine if one hybrid model is more fuel-efficient. They also will
test buses with the air-conditioning on and off.

“Metro’s fuel prices increase during the summer
because of air-conditioning, and the difference can be significant, about 20
percent,” Muncrief said.

UH researchers will “drive” the buses on the facility’s
500 horsepower AC chassis dynamometer test cell, which measures emissions and
fuel economy under controlled conditions. There won’t be any real-road testing
performed, but the dynamometer will be programmed with a bus route that runs along
Westheimer Road, complete with projected stops and starts – no speed bumps,
however.

“There is a lot of interest in this project
because of the fuel savings issue. UH has the benefit of having a chassis
dynamometer to test these large vehicles,” Muncrief said.

A total of eight Metro buses will be tested
during the two-year project. The first tests are scheduled to begin within the
first two weeks of November.

The University of Houston is a Carnegie-designated Tier One public
research university recognized by The Princeton Review as one of the nation’s
best colleges for undergraduate education. UH serves the globally competitive
Houston and Gulf Coast Region by providing world-class faculty, experiential
learning and strategic industry partnerships. Located in the nation’s
fourth-largest city, UH serves more than 38,500 students in the most ethnically
and culturally diverse region in the country.